Object of mass m rotating around a gravitation field of strength 'mu'
so-called Earth:
Centigugal force = m * V * V / R                (V is velocity and R the
radius)
Weight = mu * m / ( R * R )

In order to have equilibrium: weight = centigugal force
That means:
    V = sqrt( mu / R )

Conclusion:
higher orbit -> slower vehicle
lower orbit -> quicker vehicle
mass -> second order effect. Only if atmospheric drag is important (let us
say R < 450 km), the ratio between mass and front surface should be
considered.

ah, the question! when you are at certain altitude and want to go lower you
need to slow down your vehicle (you go to an elliptical orbit with apogee at
the initial altitude and perigee at the new target altitude, lower) and
then, when at perigee, to speed up again to reach new circular orbit of that
radius.

--------------------
Jeszs Gonzalo
Lesn (SPAIN)
--------------------
----- Original Message -----
From: "Matthew Mucker" <mmucker@AIRMAIL.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, March 24, 2001 6:13 AM
Subject: Re: [OT]:Mir


> > The orbit altitude of an object is determined by its rotational speed
> > above the earth.  If you want a higher orbit, start spinning around the
> > earth faster, lower, slow yourself down.
>
> Actually, I think this is backwards.  I'm no expert, but after reading
Gene
> Krantz' autobiography, I reacll that NASA had lots of problems with stuff
> like this until they realized that at a lower orbit, a body must revolve
> around the earch much faster to keep it in orbit.  Any experts out there
who
> can clarify?
>
> > A space station like MIR was
> > at a very low orbit to begin with, and its size would make it so it
> > could orbit much further from the earth than any satellite and still
> > orbit earth (ie, not break away).
>
> Does the size of a body have any effect on its orbit?  I know that force
is
> a constant times em-one times em-two over r-squared, but the relationship
of
> masses (earth and Mir) is probably close enough to the relationship of
Earth
> to, say, a golf ball, that there would be no difference.
>
> Just curious.
>
> -Matt
>
> --
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